One of the nation’s largest limestone mining operations has drastically reduced process downtime with a high-powered dust suppression system so efficient that a plant spokesman estimated it paid for itself during the first month of use.

By avoiding forced shutdowns due to high dust readings that had plagued the site, the portable equipment has saved thousands of dollars in lost production, while allowing reassignment of manpower previously spent handling water hoses, according to the company.

Like many mining and quarrying operations, Linwood Mining and Minerals Corp., Davenport, Iowa, had been using hoses and truck-mounted spray bars to help control dust at the crusher and transfer points, but results were always marginal. Despite their best efforts, crews could not prevent dust from becoming airborne, and every work stoppage caused by high particulate levels was costing the firm significant amounts of money.

An electronic monitor constantly samples air quality in the limestone mining area, and data is forwarded to Linwood’s control room and to the Iowa Department of Natural Resources. To comply with rigid government standards, total dust emissions from Linwood’s plant and other production facilities in the surrounding area must remain within a specified range. Any time DNR air monitor readings exceed pre-set limits, a shut-down is mandatory until the 24-hour averages return to acceptable levels.

Finding a SolutionLinwood officials visiting ConExpo/ConAgg last year came upon a booth hosted by Dust Control Technology where they saw a device called the DustBoss DB-60. The portable suppression unit is designed with special atomizing nozzles to create a fine mist of water droplets that are the optimum size for dust control, launching them great distances with a powerful 25-hp fan.

Capable of covering nearly 125,000 sq. ft. (about 1.16 hectares) when equipped with optional 359-degree oscillation, the DB-60 looked like a promising solution, and Linwood decided to rent one on a trial basis.

The unit was situated to cover the immediate area around the primary impact crusher, a Universal 4650 that reduces stone to 5-in. minus. What had been a primary source of airborne dust quickly cleared up, eliminating the periodic work stoppages on all but the windiest days, and Linwood officials saw production levels rise.

Since implementing the control system, the facility has drastically reduced shutdowns as a result of dust emissions, a welcome change from the multiple incidents each month that were typical before the DB-60 came on board. The unit’s performance was so exceptional that the company decided to purchase the machine.

In addition to the drastic reduction in airborne particles and reduced labor costs, the DustBoss has eliminated troublesome oversaturation of material. In fact, the production staff reports a noticeable improvement in product quality from eliminating the over-watering common to hand-held dust control efforts, which often create a muddy consistency that attracts contaminants and complicates handling and processing.

“Material purity is a critical issue, and you might not think dust control is part of that,” commented Plant Manager Jim Petersen. “But dirt and other contaminants contribute to the formation of air pockets in asphalt, and can also cause cracking or pop-outs on the surface of finished concrete.”

“Since it’s portable and can be aimed as needed, the DustBoss provides flexibility when dealing with the wind,” Petersen continued. “The unit’s performance has definitely met and even exceeded our requirements. We’ve run the DB-60 over the dustiest materials we process, and it’s done exactly what we’ve needed it to.” Linwood's facility is a full-time operation, producing as much as 2 million tons of limestone products each year. The plant features four kilns, two of which are fully automated, and all processing is carefully monitored by computer control.”

Information for this article courtesy of Dust Control Technology.

Linwood LineageLinwood Mining and Minerals Corp. has been a producer of lime products, aggregates and calcium carbonate since 1944, and currently ranks as one of the largest limestone mining operations in the U.S. Linwood originally operated as an open-cut limestone quarry. However, because of demand for the uniqueness and high purity of the company's limestone and exceptionally pure calcium carbonate, mining was extended to an underground operation.

As demand for Linwood's products increased through the years, the company introduced new equipment and technology to accommodate expansion of the mines and meet customer requirements.

With a confirmed reserve of more than 400 million tons, Linwood is assured of the ability to operate at high capacity well into the future. The company is uniquely situated in the Midwest, capable of shipping its products by truck, rail or barge.

Dust Control Technology said that its DustBoss product line helps reduce labor costs versus manual sprays, freeing up manpower for more important tasks. The automated units also use less water than hoses and sprinklers, with some customers realizing payback in less than six months and netting an annual cost savings of more than $50,000.